Caption: Fossil formation. Sequential artwork of the formation of a dinosaur fossil. The process begins when the dinosaur dies and the body ends up in a location where fossilisation is possible, here in sediments below water (upper left). The soft tissues decay, while minerals in the dinosaur's skeleton are gradually replaced by minerals from the mud. These minerals solidify into a form of stone or rock, preserving the shape and structure of the skeleton (upper right). The fossil may remain underground, or may eventually be exposed by erosion of the surrounding material (lower centre).